Tear gas is a term used to refer to any of a number of chemical compounds that cause tears and pain in the eyes and sometimes temporary blindness. Another term that is commonly used to describe tear gas is lachrymatory agent. Tear gas can be used for self-defense, but it is more commonly used as a riot control agent and as a chemical weapon. (Carron 2009) Tear gas irritates the mucous membranes of the eyes, nose, mouth, and lungs. The irritation may be caused by a chemical reaction with the sulfhydryl group of enzymes, though other mechanisms also occur. The results of exposure are coughing, sneezing, and tearing. Tear gas generally is non-lethal, but some agents are toxic. (Hu 1989) Actually, tear gas agents aren't usually gases. Most compounds used as lachrymatory agents are solids at room temperature. They are suspended in solution and sprayed as aerosols or in grenades.
Various Types
Many types of tear gas and other riot control agents have been produced with various degrees of effects. The CN and CS types are the most widely used and known, but around 15 different types of tear gas have been developed worldwide e.g. adamsite or bromoacetone, CNB, and CNC. CS has become the most popular due to its strong effect and lack of toxicity in comparison with other similar chemical agents. The three oldest types of tear gas are xylyl bromide, CN and CS. (Beswick 1983) Xylyl bromide shown here:
Fig 1: ortho, meta and para xylyl bromide
is a clear liquid was first used in 1914 and was widely used throughout World War I because it was easily made. It has since been drastically reduced in usage, however, due to it being extremely toxic. (Duffy 2009) CN gas or chloroacetophenone shown here:
Fig 2: CN gas
is the oldest chemical lachrymator being first synthesized in 1871. As with xylyl bromide, it was first used as a tear gas in World War I. It also has been used less over the due to its toxicity. It is less toxic than xylyl bromide but still more so than CS. While it is still scarcely used as a tear gas agent it is still common to find it used for self-defense purposes in the form of mace. (Treudler 1999) The third and most commonly used tear gas is CS gas shown here:
Fig 3: CS gas
It is a cyanocarbon and was discovered in 1928. CS gas is the common name given to the compound 2-chlorobenzalmalononitrile. It got its name from the two Americans that discovered it, Ben Corson and Roger Stoughton, taking the first letters of their last names. (Corson 1928) It is generally accepted as being non-lethal therefore making it an optimal choice for riot control. It was first tested on animals, where it was discovered that it had only a small effect on them because most animals have less developed tear-ducts than humans as well as fur to protect them. (Upshall 1973) This also made it a much better choice for a lachrymatory agent because they didn't have to worry as much about harmful wildlife with it when it was released out in the open.
Synthesis
CN is synthesized using Friedel-Crafts acylation:
Fig 4: Basic Friedel Crafts Alkylation
where an aromatic ring undergoes acylation with an alkyl chloride using a strong Lewis acid as a catalyst, usually aluminum chloride. (Groves 1972)
The specific CN reaction is done by reacting benzene with chloroacteyl chloride using the normal aluminum chloride catalyst:
Fig 5: Synthesis of CN
(Kamal 2003)
CS is synthesized the Knoevenagel condensation:
Fig 6: Basic Knoevenagel condensation
The Knoevenagel condensation is named after Emil Knoevenagel and is a modified aldol condensation. It begins with a nucleophilic addition of an active hydrogen to a carbonyl group and ends with a dehydration step to form an alpha, beta conjugated enone, shown above. The reaction requires the carbonyl compound to be an aldehyde or ketone and the hydrogen component has the form Z-CH2-Z. In the case of CS gas it is the aldehyde 2-chlorobenzaldehyde and the nitrile malononitrile where the Z groups are the electron withdrawing cyano groups. The reaction is catalyzed with a weak base like pyridine. This is so that the aldehyde doesn't induce self-condensation. (Knoevenagel 1898) The specific reaction of CS gas is:
ClC6H4CHO + H2C(CN)2 → ClC6H4CHC(CN)2 + H2O
Fig 7: Synthesis of CS
The production method has not changed since the substance was discovered by Corson and Stoughton. They also made it clear that the substance is harmless when wet, but that even handling the powder before it has been aerosolized can cause severe sneezing and trying to wash it off once it gets on the face only intensifies the discomfort. (Corson, 1928) Once the solid white 2-chlorobenzalmalononitrile is synthesized it must be changed again to allow it to be used as an aerosol. Several of the techniques used to make CS usable are to melt it down and spray it in molten form, dissolve it in some organic solvent and let it evaporate, a CS2 dry powder, which is a siliconized form of CS, and CS from thermal grenades which cause instant vaporization. (Hu 1989)
What it does
The effect of CS on a person will depend on whether it is packaged as a solution or used as an aerosol. The size of solution droplets and the size of the CS particulates after evaporation are factors determining its effect on the human body. (Park 1972) The chemical reacts with moisture on the skin and in the eyes, causing a burning sensation and the immediate forceful and uncontrollable shutting of the eyes. (Committees 1999) Effects usually include tears streaming from the eyes causing blurred vision, profuse coughing, exceptional nasal discharge that is full of mucus, burning in the eyes, eyelids, nose and throat areas, disorientation and confusion including anger, dizziness, restricted breathing including a feeling of choking,vomiting and prostration. Some of the more severe effects only present in highly concentrated doses. It may also cause the skin where sweaty and or sunburned to develop a kind of chemical rash. (Debarre 1999) Almost all of the immediate effects wear off within an hour (such as exceptional nasal discharge and profuse coughing), although the feeling of burning and highly irritated skin may persist for hours. Affected clothing will need to be washed several times or thrown away. Tear gas is generally used to control riots, disperse crowds, and subdue individuals. (Danto 1987) It is intended to cause pain, so while many of the symptoms are unpleasant it is doing what it what intended for. The disorientation and confusion it causes may not be totally psychological either. In some cases, the solvent used to prepare the tear gas may contribute to the reaction and may be more toxic than the tear gas agent itself. Tear gas usually is delivered in the form a grenade, which is fitted onto the end of a gas gun and fired with a blank shotgun cartridge. Tear gas grenades often explode in the air, delivering a metal container which will spew gas. (Bhattacharya 1993)
Toxicity
Even though CS is accepted as being non-lethal there have been several people who have raised doubts about the classification. Various studies have been conducted showing that in addition to pulmonary harm, CS gas can also cause the heart and liver to be damaged. (Marrs 1983) It was discovered that given two factors, CS could be deemed lethal. The factors are one if no gas masks are being used and two tin the targets are enclosed in a room. Only if both of these risk factors occur is there a chance of death. (Jones 1970) CS exposure has also been linked to high rates of miscarriages. This is mainly due to the gas’ effect on mammalian cells. When it starts to become metabolized, it is revealed that cyanide can be found in human tissue. (Hu 1989)
A study was done by Cole et al. in the journal of experimental physiology investigating the effects of CS gas and ammonia on subjects through their heart rate while they exercised. They would let them exercise without exposure then on another day expose them and see the difference. Looking just at the CS portion, all subjects experienced intense discomfort on first exposure to the aerosol including cough, lacrimation and sub sternal pain. (Cole 1977) In most instances this wore off within a few minutes; however in the study, two subjects withdrew one before and one after the first period of exercise and two subjects were unable to complete the first period on account of coughing which coincided with ignition of CS generators. These subjects were able to complete the second period without incident. The findings reported for the study relate to the pooled results for the first and second periods of exercise in the remaining seven subjects for whom complete data were obtained. Analysis of the incomplete data for the other subjects yielded comparable results. For the study, the exercise cardiac frequency was higher during exposure to CS than on the control day. The increase was associated with a higher ambient temperature. When temperature was allowed for by correcting the cardiac frequency to the arbitrary temperature of 20°C, the difference in cardiac frequency was eliminated. The ventilation minute volume was reduced by exposure to CS compared with breathing air. (Cole 1977)
Caption: Fig 8: Data from Cole's experiment (Cole 1977)
In short what this is trying to say is that as expected, once someone has been exposed to CS gas they have a very hard time trying to perform any kind of physical activity as it causes their heart to need a lot more oxygen uptake to function. This shows a good explanation for how tear gas incapacitates people. If they are unable to perform physical activities, then they are less of a threat to law enforcement.
Treatment
The best defense against tear gas is a gas mask, but without one, a bandana or paper towel can be soaked in lemon juice or cider vinegar and stored it in a plastic baggie until the gas is encountered. Breathing through the acidified cloth for several minutes should give sufficient time to get upwind or reach higher ground. (Viala 2005) Contacts shouldn’t be worn anywhere that tear gas may be encountered. They should be immediately removed them because once the gas is absorbed into the lens it will never come out and can cause severe damage to the eye. Clothes can be worn again after they are washed, but they should be washed separately the first time. This washing should be done in an alkaline solution of water mixed with 5% sodium bisulfite. (Euripidou 2004) It is also possible to avoid exposure by breathing the air inside of a shirt, since there is less air circulation and therefore a lower concentration of the gas, but that is counterproductive once the fabric becomes saturated. First aid for eyes is to flush them with sterile saline or water until the stinging starts to abate. Exposed skin should be washed with soap and water. Breathing difficulties are treated by administering oxygen and in some cases using medication that are used to treat asthma. Medicated bandages can be used on burns. (Viala 2005)
Conclusion
Tear gas is such a widely used tool that in some ways it’s hard to believe that there is so much confusion and discussion over it. People have been debating about whether or not it’s ethical to use since it was discovered, but it’s never been in question that it is effective. It is very good at what it does and that is to simply incapacitate people. I believe if used outdoors and the type is CS gas, that it is completely safe for use. It may make someone uncomfortable for a few hours, but again that’s the point. I do agree however that the risk that comes with using it in enclosed spaces should be explored further before any kind of strict conclusions are drawn. Until those studies are done it would probably be best to ere on the side of caution and just not use it inside. Even so it’s the best available weapon for crowd control so unless something remarkably better comes along police forces are going to continue to use it.
Carron, P.-N., & Yersin, B. (2009). Management of the effects of exposure to tear gas. Bmj, 338, 1554–1558. http://dx.doi.org/10.1136/bmj.b2283
Cole, T. J., Cotes, J. E., Johnson, G. R., Martin, H.V., Reed, J. W., Saunders, M.J. (1977). Ventilation, Cardiac Frequency and Pattern of Breathing During Exercise in Men Exposed to o-chlorobenzylidene malononitrile (CS) and Ammonia Gas in Low Concentrations. Quarterly Journal of Experimental Physiology, 62, 341–351. http://ep.physoc.org/content/62/4/341.long
Committees on Toxicity, Mutagenicity and Carcinogenicity of Chemicals in Food, Consumer Products and The Environment. (1999). Statement on 2-chlorobenzylidene malononitrile (CS) and CS Spray. Department of Health. http://cot.food.gov.uk/pdfs/csgas.pdf
Corson, B. B., & Stoughton, R. W. (1928). Reactions of Alpha, Beta-Unsaturated Dinitriles. Journal of the American Chemical Society, 50(10), 2825–2837. http://dx.doi.org/10.1021/ja01397a037
Danto, B. L. (1987). Medical Problems and Criteria Regarding the Use of Tear Gas by Police. American Journal of Forensic Meidcine & Pathology, 8(4), 317–322. http://dx.doi.org/10.1097/00000433-198712000-00011
Debarre, S., Karinthi, L., Delamanche, S., Fuché, C., Desforges, P., & Calvet, J.-H. (1999). Comparative acute toxicity of o-chlorobenzylidene malononitrile (CS) and oleoresin capsicum (OC) in awake rats. Human & Experimental Toxicology, 18(12), 724–730. http://dx.doi.org/10.1191/096032799678839617
Euripidou, E., MacLehose, R., & Fletcher, a. (2004). An investigation into the short term and medium term health impacts of personal incapacitant sprays. A follow up of patients reported to the National Poisons Information Service (London). Emergency medicine journal : EMJ, 21(5), 548–52. http://dx.doi.org/10.1136/emj.2003.012773
Jones, G. R. N., & Israel, M. S. (1970). Mechanism of Toxicity of Injected CS Gas. Nature, 228(5278), 1315–1317. http://dx.doi.org/10.1038/2281315a0
Kamal, A., Sandbhor, M., Ahmed, K., Adil, S. F., & Shaik, A. A. (2003). Chemoenzymatic synthesis of enantiomerically pure terminal 1,2-diols. Tetrahedron: Asymmetry, 14(21), 3861–3866. http://dx.doi.org/10.1016/j.tetasy.2003.09.035
Knoevenagel, E. (1898). Condensation von Malonsäure mit aromatischen Aldehyden durch Ammoniak und Amine. European Journal of Inorganic Chemistry, 31(3), 2596–2619. http://dx.doi.org/10.1002/cber.18980310308
Marrs, T. C., Colgrave, H. F., Cross, N. L., Gazzard, M. F., & Brown, R. F. (1983). A repeated dose study of the toxicity of inhaled 2-chlorobenzylidene malononitrile (CS) aerosol in three species of laboratory animal. Archives of toxicology, 52(3), 183–198. http://dx.doi.org/10.1007/BF00333898
Park, S., & Giammona, S. T. (1972). Toxic Effects of Tear Gas on an Infant Following Prolonged Exposure. Archives of Pediatrics & Adolescent Medicine, 123(3), 245–246. http://dx.doi.org/10.1001/archpedi.1972.02110090115018
Treudler, R., Tebbe, B., Blume-Peytavi, U., Krasagakis, K., & Orfanos, C. E. (1999). Occupational contact dermatitis due to 2-chloracetophenone tear gas. British Journal of Dermatology, 140(3), 531–534. http://dx.doi.org/10.1046/j.1365-2133.1999.02724.x
Upshall, D. G. (1973). Effects of o-chlorobenzylidene malononitrile (CS) and the stress of aerosol inhalation upon rat and rabbit embryonic development. Toxicology and Applied Pharmacology, 24(1), 45–59. http://dx.doi.org/10.1016/0041-008X(73)90180-4
Viala, B., Blomet, J., Mathieu, L., & Hall, A. H. (2005). Prevention of CS “Tear Gas” Eye and Skin Effects and Active Decontamination with Diphoterine: Preliminary Studies in 5 French Gendarmes. The Journal of Emergency Medicine, 29(1), 5–8. http://dx.doi.org/10.1016/j.jemermed.2005.01.002
A Look at the Various Aspects of Tear Gas
Background
Tear gas is a term used to refer to any of a number of chemical compounds that cause tears and pain in the eyes and sometimes temporary blindness. Another term that is commonly used to describe tear gas is lachrymatory agent. Tear gas can be used for self-defense, but it is more commonly used as a riot control agent and as a chemical weapon. (Carron 2009) Tear gas irritates the mucous membranes of the eyes, nose, mouth, and lungs. The irritation may be caused by a chemical reaction with the sulfhydryl group of enzymes, though other mechanisms also occur. The results of exposure are coughing, sneezing, and tearing. Tear gas generally is non-lethal, but some agents are toxic. (Hu 1989) Actually, tear gas agents aren't usually gases. Most compounds used as lachrymatory agents are solids at room temperature. They are suspended in solution and sprayed as aerosols or in grenades.Various Types
Many types of tear gas and other riot control agents have been produced with various degrees of effects. The CN and CS types are the most widely used and known, but around 15 different types of tear gas have been developed worldwide e.g. adamsite or bromoacetone, CNB, and CNC. CS has become the most popular due to its strong effect and lack of toxicity in comparison with other similar chemical agents. The three oldest types of tear gas are xylyl bromide, CN and CS. (Beswick 1983) Xylyl bromide shown here:is a clear liquid was first used in 1914 and was widely used throughout World War I because it was easily made. It has since been drastically reduced in usage, however, due to it being extremely toxic. (Duffy 2009) CN gas or chloroacetophenone shown here:
is the oldest chemical lachrymator being first synthesized in 1871. As with xylyl bromide, it was first used as a tear gas in World War I. It also has been used less over the due to its toxicity. It is less toxic than xylyl bromide but still more so than CS. While it is still scarcely used as a tear gas agent it is still common to find it used for self-defense purposes in the form of mace. (Treudler 1999) The third and most commonly used tear gas is CS gas shown here:
It is a cyanocarbon and was discovered in 1928. CS gas is the common name given to the compound 2-chlorobenzalmalononitrile. It got its name from the two Americans that discovered it, Ben Corson and Roger Stoughton, taking the first letters of their last names. (Corson 1928) It is generally accepted as being non-lethal therefore making it an optimal choice for riot control. It was first tested on animals, where it was discovered that it had only a small effect on them because most animals have less developed tear-ducts than humans as well as fur to protect them. (Upshall 1973) This also made it a much better choice for a lachrymatory agent because they didn't have to worry as much about harmful wildlife with it when it was released out in the open.
Synthesis
CN is synthesized using Friedel-Crafts acylation:where an aromatic ring undergoes acylation with an alkyl chloride using a strong Lewis acid as a catalyst, usually aluminum chloride. (Groves 1972)
The specific CN reaction is done by reacting benzene with chloroacteyl chloride using the normal aluminum chloride catalyst:
(Kamal 2003)
CS is synthesized the Knoevenagel condensation:
The Knoevenagel condensation is named after Emil Knoevenagel and is a modified aldol condensation. It begins with a nucleophilic addition of an active hydrogen to a carbonyl group and ends with a dehydration step to form an alpha, beta conjugated enone, shown above. The reaction requires the carbonyl compound to be an aldehyde or ketone and the hydrogen component has the form Z-CH2-Z. In the case of CS gas it is the aldehyde 2-chlorobenzaldehyde and the nitrile malononitrile where the Z groups are the electron withdrawing cyano groups. The reaction is catalyzed with a weak base like pyridine. This is so that the aldehyde doesn't induce self-condensation. (Knoevenagel 1898) The specific reaction of CS gas is:
ClC6H4CHO + H2C(CN)2 → ClC6H4CHC(CN)2 + H2O
The production method has not changed since the substance was discovered by Corson and Stoughton. They also made it clear that the substance is harmless when wet, but that even handling the powder before it has been aerosolized can cause severe sneezing and trying to wash it off once it gets on the face only intensifies the discomfort. (Corson, 1928) Once the solid white 2-chlorobenzalmalononitrile is synthesized it must be changed again to allow it to be used as an aerosol. Several of the techniques used to make CS usable are to melt it down and spray it in molten form, dissolve it in some organic solvent and let it evaporate, a CS2 dry powder, which is a siliconized form of CS, and CS from thermal grenades which cause instant vaporization. (Hu 1989)
What it does
The effect of CS on a person will depend on whether it is packaged as a solution or used as an aerosol. The size of solution droplets and the size of the CS particulates after evaporation are factors determining its effect on the human body. (Park 1972) The chemical reacts with moisture on the skin and in the eyes, causing a burning sensation and the immediate forceful and uncontrollable shutting of the eyes. (Committees 1999) Effects usually include tears streaming from the eyes causing blurred vision, profuse coughing, exceptional nasal discharge that is full of mucus, burning in the eyes, eyelids, nose and throat areas, disorientation and confusion including anger, dizziness, restricted breathing including a feeling of choking,vomiting and prostration. Some of the more severe effects only present in highly concentrated doses. It may also cause the skin where sweaty and or sunburned to develop a kind of chemical rash. (Debarre 1999) Almost all of the immediate effects wear off within an hour (such as exceptional nasal discharge and profuse coughing), although the feeling of burning and highly irritated skin may persist for hours. Affected clothing will need to be washed several times or thrown away. Tear gas is generally used to control riots, disperse crowds, and subdue individuals. (Danto 1987) It is intended to cause pain, so while many of the symptoms are unpleasant it is doing what it what intended for. The disorientation and confusion it causes may not be totally psychological either. In some cases, the solvent used to prepare the tear gas may contribute to the reaction and may be more toxic than the tear gas agent itself. Tear gas usually is delivered in the form a grenade, which is fitted onto the end of a gas gun and fired with a blank shotgun cartridge. Tear gas grenades often explode in the air, delivering a metal container which will spew gas. (Bhattacharya 1993)Toxicity
Even though CS is accepted as being non-lethal there have been several people who have raised doubts about the classification. Various studies have been conducted showing that in addition to pulmonary harm, CS gas can also cause the heart and liver to be damaged. (Marrs 1983) It was discovered that given two factors, CS could be deemed lethal. The factors are one if no gas masks are being used and two tin the targets are enclosed in a room. Only if both of these risk factors occur is there a chance of death. (Jones 1970) CS exposure has also been linked to high rates of miscarriages. This is mainly due to the gas’ effect on mammalian cells. When it starts to become metabolized, it is revealed that cyanide can be found in human tissue. (Hu 1989)A study was done by Cole et al. in the journal of experimental physiology investigating the effects of CS gas and ammonia on subjects through their heart rate while they exercised. They would let them exercise without exposure then on another day expose them and see the difference. Looking just at the CS portion, all subjects experienced intense discomfort on first exposure to the aerosol including cough, lacrimation and sub sternal pain. (Cole 1977) In most instances this wore off within a few minutes; however in the study, two subjects withdrew one before and one after the first period of exercise and two subjects were unable to complete the first period on account of coughing which coincided with ignition of CS generators. These subjects were able to complete the second period without incident. The findings reported for the study relate to the pooled results for the first and second periods of exercise in the remaining seven subjects for whom complete data were obtained. Analysis of the incomplete data for the other subjects yielded comparable results. For the study, the exercise cardiac frequency was higher during exposure to CS than on the control day. The increase was associated with a higher ambient temperature. When temperature was allowed for by correcting the cardiac frequency to the arbitrary temperature of 20°C, the difference in cardiac frequency was eliminated. The ventilation minute volume was reduced by exposure to CS compared with breathing air. (Cole 1977)
In short what this is trying to say is that as expected, once someone has been exposed to CS gas they have a very hard time trying to perform any kind of physical activity as it causes their heart to need a lot more oxygen uptake to function. This shows a good explanation for how tear gas incapacitates people. If they are unable to perform physical activities, then they are less of a threat to law enforcement.
Treatment
The best defense against tear gas is a gas mask, but without one, a bandana or paper towel can be soaked in lemon juice or cider vinegar and stored it in a plastic baggie until the gas is encountered. Breathing through the acidified cloth for several minutes should give sufficient time to get upwind or reach higher ground. (Viala 2005) Contacts shouldn’t be worn anywhere that tear gas may be encountered. They should be immediately removed them because once the gas is absorbed into the lens it will never come out and can cause severe damage to the eye. Clothes can be worn again after they are washed, but they should be washed separately the first time. This washing should be done in an alkaline solution of water mixed with 5% sodium bisulfite. (Euripidou 2004) It is also possible to avoid exposure by breathing the air inside of a shirt, since there is less air circulation and therefore a lower concentration of the gas, but that is counterproductive once the fabric becomes saturated. First aid for eyes is to flush them with sterile saline or water until the stinging starts to abate. Exposed skin should be washed with soap and water. Breathing difficulties are treated by administering oxygen and in some cases using medication that are used to treat asthma. Medicated bandages can be used on burns. (Viala 2005)Conclusion
Tear gas is such a widely used tool that in some ways it’s hard to believe that there is so much confusion and discussion over it. People have been debating about whether or not it’s ethical to use since it was discovered, but it’s never been in question that it is effective. It is very good at what it does and that is to simply incapacitate people. I believe if used outdoors and the type is CS gas, that it is completely safe for use. It may make someone uncomfortable for a few hours, but again that’s the point. I do agree however that the risk that comes with using it in enclosed spaces should be explored further before any kind of strict conclusions are drawn. Until those studies are done it would probably be best to ere on the side of caution and just not use it inside. Even so it’s the best available weapon for crowd control so unless something remarkably better comes along police forces are going to continue to use it.References
Beswick, F. W. (1983). Chemical Agents used in Riot Control and Warfare. Human & Experimental Toxicology, 2(2), 247–256. http://dx.doi.org/10.1177/096032718300200213Bhattacharya, S. T., & Hayward, A. W. (1993). CS gas-implications for the anaesthetist. Anaesthesia, 48(January), 896–897. http://dx.doi.org/10.1111/j.1365-2044.1993.tb07424.x
Carron, P.-N., & Yersin, B. (2009). Management of the effects of exposure to tear gas. Bmj, 338, 1554–1558. http://dx.doi.org/10.1136/bmj.b2283
Cole, T. J., Cotes, J. E., Johnson, G. R., Martin, H.V., Reed, J. W., Saunders, M.J. (1977). Ventilation, Cardiac Frequency and Pattern of Breathing During Exercise in Men Exposed to o-chlorobenzylidene malononitrile (CS) and Ammonia Gas in Low Concentrations. Quarterly Journal of Experimental Physiology, 62, 341–351. http://ep.physoc.org/content/62/4/341.long
Committees on Toxicity, Mutagenicity and Carcinogenicity of Chemicals in Food, Consumer Products and The Environment. (1999). Statement on 2-chlorobenzylidene malononitrile (CS) and CS Spray. Department of Health. http://cot.food.gov.uk/pdfs/csgas.pdf
Corson, B. B., & Stoughton, R. W. (1928). Reactions of Alpha, Beta-Unsaturated Dinitriles. Journal of the American Chemical Society, 50(10), 2825–2837. http://dx.doi.org/10.1021/ja01397a037
Danto, B. L. (1987). Medical Problems and Criteria Regarding the Use of Tear Gas by Police. American Journal of Forensic Meidcine & Pathology, 8(4), 317–322. http://dx.doi.org/10.1097/00000433-198712000-00011
Debarre, S., Karinthi, L., Delamanche, S., Fuché, C., Desforges, P., & Calvet, J.-H. (1999). Comparative acute toxicity of o-chlorobenzylidene malononitrile (CS) and oleoresin capsicum (OC) in awake rats. Human & Experimental Toxicology, 18(12), 724–730. http://dx.doi.org/10.1191/096032799678839617
Duffy, M. (2009). Weapons of War - Poison Gas. firstworldwar.com. Retrieved 2012-12-05. http://www.firstworldwar.com/weaponry/gas.htm
Euripidou, E., MacLehose, R., & Fletcher, a. (2004). An investigation into the short term and medium term health impacts of personal incapacitant sprays. A follow up of patients reported to the National Poisons Information Service (London). Emergency medicine journal : EMJ, 21(5), 548–52. http://dx.doi.org/10.1136/emj.2003.012773
Groves, J. K. (1972). The Friedel-Crafts Acylation of Alkenes. Chemical Society Reviews, (1), 73–97. http://dx.doi.org/10.1039/CS9720100073
Hu, H., Fine, J., Epstein, P., Kelsey, K., Reynolds, P., & Walker, B. (1989). Tear Gas-Harassing Agent or Toxic Chemical Weapon? Journal of the American Medical Association, 262, 660–663. http://dx.doi.org/10.1001/jama.1989.03430050076030 green access http://desastres.usac.edu.gt/documentos/pdf/eng/doc8080/doc8080-contenido.pdf
Jones, G. R. N., & Israel, M. S. (1970). Mechanism of Toxicity of Injected CS Gas. Nature, 228(5278), 1315–1317. http://dx.doi.org/10.1038/2281315a0
Kamal, A., Sandbhor, M., Ahmed, K., Adil, S. F., & Shaik, A. A. (2003). Chemoenzymatic synthesis of enantiomerically pure terminal 1,2-diols. Tetrahedron: Asymmetry, 14(21), 3861–3866. http://dx.doi.org/10.1016/j.tetasy.2003.09.035
Knoevenagel, E. (1898). Condensation von Malonsäure mit aromatischen Aldehyden durch Ammoniak und Amine. European Journal of Inorganic Chemistry, 31(3), 2596–2619. http://dx.doi.org/10.1002/cber.18980310308
Marrs, T. C., Colgrave, H. F., Cross, N. L., Gazzard, M. F., & Brown, R. F. (1983). A repeated dose study of the toxicity of inhaled 2-chlorobenzylidene malononitrile (CS) aerosol in three species of laboratory animal. Archives of toxicology, 52(3), 183–198. http://dx.doi.org/10.1007/BF00333898
Park, S., & Giammona, S. T. (1972). Toxic Effects of Tear Gas on an Infant Following Prolonged Exposure. Archives of Pediatrics & Adolescent Medicine, 123(3), 245–246. http://dx.doi.org/10.1001/archpedi.1972.02110090115018
Treudler, R., Tebbe, B., Blume-Peytavi, U., Krasagakis, K., & Orfanos, C. E. (1999). Occupational contact dermatitis due to 2-chloracetophenone tear gas. British Journal of Dermatology, 140(3), 531–534. http://dx.doi.org/10.1046/j.1365-2133.1999.02724.x
Upshall, D. G. (1973). Effects of o-chlorobenzylidene malononitrile (CS) and the stress of aerosol inhalation upon rat and rabbit embryonic development. Toxicology and Applied Pharmacology, 24(1), 45–59. http://dx.doi.org/10.1016/0041-008X(73)90180-4
Viala, B., Blomet, J., Mathieu, L., & Hall, A. H. (2005). Prevention of CS “Tear Gas” Eye and Skin Effects and Active Decontamination with Diphoterine: Preliminary Studies in 5 French Gendarmes. The Journal of Emergency Medicine, 29(1), 5–8. http://dx.doi.org/10.1016/j.jemermed.2005.01.002